Patch adapted from upstream c3915bb99638c1ccf57217097b14b5db69bcac96
by Milan Crha:

    PrintableOptions.cmake: Correct variable name comparison
    
    CMake 3.20.1 errors out with:
    
    CMake Error at cmake/modules/PrintableOptions.cmake:38 (message):
       variable name cannot be empty
     Call Stack (most recent call first):
       CMakeLists.txt:152 (add_printable_variable)
    
    Change how the parameter value is compared, to fix it.

--- a/cmake/modules/PrintableOptions.cmake
+++ b/cmake/modules/PrintableOptions.cmake
@@ -19,32 +19,32 @@
 #    prints all the build options previously added with the above functions
 
 macro(add_printable_variable_bare _name)
-	if(_name STREQUAL "")
+	if("${_name}" STREQUAL "")
 		message(FATAL_ERROR "variable name cannot be empty")
-	endif(_name STREQUAL "")
+	endif("${_name}" STREQUAL "")
 	list(APPEND _printable_options ${_name})
 endmacro()
 
 macro(add_printable_option _name _description _default_value)
-	if(_name STREQUAL "")
+	if("${_name}" STREQUAL "")
 		message(FATAL_ERROR "option name cannot be empty")
-	endif(_name STREQUAL "")
+	endif("${_name}" STREQUAL "")
 	option(${_name} ${_description} ${_default_value})
 	add_printable_variable_bare(${_name})
 endmacro()
 
 macro(add_printable_variable _name _description _default_value)
-	if(_name STREQUAL "")
+	if("${_name}" STREQUAL "")
 		message(FATAL_ERROR "variable name cannot be empty")
-	endif(_name STREQUAL "")
+	endif("${_name}" STREQUAL "")
 	set(${_name} ${_default_value} CACHE STRING ${_description})
 	add_printable_variable_bare(${_name})
 endmacro()
 
 macro(add_printable_variable_path _name _description _default_value)
-	if(_name STREQUAL "")
+	if("${_name}" STREQUAL "")
 		message(FATAL_ERROR "path variable name cannot be empty")
-	endif(_name STREQUAL "")
+	endif("${_name}" STREQUAL "")
 	set(${_name} ${_default_value} CACHE PATH ${_description})
 	add_printable_variable_bare(${_name})
 endmacro()
